Abstract: A new family of parameters intended for composition studies is presented.They make exclusive use of surface data combining the information from thetotal signal at each triggered detector and the array geometry. We perform ananalytical study of these composition estimators in order to assess theirreliability, stability and possible optimization. The influence of thedifferent slopes of the proton and Iron lateral distribution function on thediscrimination power of the estimators is also studied. Additionally, thestability of the parameter in face of a possible underestimation of the size ofthe muon component by the shower simulation codes, as it is suggested byexperimental evidence, is also studied.